Weird problem on '02 3.4L V6 auto
Rod you may know the answer to this one but it has me stumped.
Ok, first in neutral there is a 4000 rpm rev-limiter. Now car forums state this is to protect the engine, which in my mind is absurd. If an engine redlines at 5500 then it is regardless of load because the damn thing is still turning 5500 RPMs. One guy in the forum said something that made sense. He said GM put it there to prevent people (idiots) from neutral dropping the tranny at high RPMs. I had a friend that did this in an '89 Pontiac Grand Am and very soon his tranny went to crapola. So what is the 4000 RPM neutral rev limiter for? And if this is so important then why the hell does my Mitsubish Eclipse, former Pontiac Grand Am, and Eagle Talon allow you to rev to the red in all gears? Seems to me redline is redline - just don't go over it and besides the stock computer won't let you.
So is GM just protecting warranty costs for replacing drivetrains due to misuse and neutral drops or is this blown engine argument valid? Being a car tuner and having seen 3000 RPM stalls, I say the former is a bunch of hogwash.
Now for the problem, hopefully unrelated to the 4000 rpm rev limit. As you begin to accelerate the car does not want to shift correctly. If you lay into the gas it will stay in gear and just rev, but the rev's will never go over 4000. On the speedo, the redline is 5500 RPMs. I know the fuel cut-off for this car is 6000 RPMs. Why the hell is it limiting at 4000?
Second, when you merge onto the highway you must actually release gas pressure to get the tranny to shift correctly. Then the slightest change in pressure makes it seem like the tranny can't decide what gear to get into. Most of the time it bogs the engine so bad it accels like a turtle.
Third, if you lay into the gas on the highway it seems to kick out of OD, downshift, downshift and accel with no problem. However if you floor it, it goes back into the aforementioned gear that just sits there at 4000 RPM with no acceleration whatsoever.
Now if the tranny wasn't shifting and that was the problem, the car would rev out and continue revving until it reached redline at which point the computer would fuel cut. Similar to never clutching and shifting in a manual. No shift, just RPM and no power because you are out of the power band for that gear. So my idea is that the computer is limiting the rev at 4000 and thus the fluid pressure in the tranny is not adequate enough to shift correctly. Now it is possible that the tranny is downshifting too far and the engine actually does not have enough horsepower to push the revs over 4000 RPM in that gear.......but I highly doubt it. It's a Monte Carlo 3.4L V6 and while it's not the 3800, it still has about 165 to 175 hp. That's enough to wrap every gear out.
Shouldn't an auto tranny wrap every gear out if you keep the gas on the floor? It will wrap, shift, wrap, shift, etc..
Could a faulty rev limiter cause these types of tranny problems?
I've never seen this. I got into my Eclipse and ran the crapola out of it (it's a stick BTW) and it fuel-cuts at 5900 RPM. But the engine is solid, doesn't leak, and performs well even in high RPM ranges. I guess that's the diff between GM and Mits eh.
Please help anyone.